CHAPTER IX 

 VIRUSES AND NUCLEIC ACIDS 



1. Nucleic Acids in Virus Particles 



At present it is generally believed that viruses are nucleoproteins, 

 and nucleic acids are customarily considered as being indispensable for 

 viruses. However, if writer's opinion so far discussed as regards the 

 viruses is legitimate, it may be said that nucleic acids are not always 

 .necessary for the virus action. Since the template of viruses to be 

 replicated in the host protoplasm should be involved in the structure 

 of globulin-like proteins, there appears to be no need to assume nucleic 

 acids as being indispensable for the template action. 



In his splendid book "Plant Viruses and Virus Diseases" Bawden 

 stated as follows: "In spite of the wide differences between the pro- 

 perties of the individual viruses so far purified, it would be rash to 

 assume that they form a random and representative sample of the 

 whole group. Because these are chemically similar, it can almost 

 be taken for granted that some other viruses are also nucleoproteins, 

 but to assume that all are would be decidedly premature. The methods 

 of isolation so far used may be acting as a selective agency, succeeding 

 only with those that are nucleoproteins." 



If nucleic acids were essential components for viruses, their content 

 and kind would be expected to be constant to a certain extent, but the 

 fact is that they are unusually variable. Among many viruses studied 

 so far phage appears to have the highest content of nucleic acid, and 

 by Taylor (151) it has been estimated to be so high as nearly 50 per 

 ■cent, whereas Newcastle disease virus has been reported to contain a 

 quantity of nonlipid phosphorus equivalent to only about 1 per cent 

 nucleic acid (152). Chemical compositions of various viruses are shown 

 in Table 6; also from this Table it is evident that there are great differ- 

 ences in nucleic acids both in kind and content. 



The writer has assumed as already stated that in the usual virus 

 partcles as well as in the protoplasm, stretched peptide chains of protein 

 molecules having the nature of euglobulin are arranged in parallel 

 alignment, and lipids being inserted among the peptide chains. Nucleic 

 acids, if contained any, are considered to be inserted, like the lipids, 

 among the stretched protein molecules. X-ray analysis of tobacco-mosaic 



